Adjustable support column for a pivotal chair

ABSTRACT

An adjustable support column for pivotally mounting the seat section of a chair to the base portion thereof. The nave of the base portion has an upwardly flared bore into which the lower, tapered end portion of a sheath tube is supportingly received. A thrust bearing is mounted inside the lower end portion of the sheath tube and rotatably supports an adjusting screw. The seat section has a conical spindle that is received within a conical socket at the upper end of the spindle tube. A bushing is fixed to the lower end portion of the spindle tube and is threaded onto the adjusting screw. The bearing and bushing are selected such that the bearing offers less resistance to relative rotation between the adjusting screw and the sheath tube than the bushing offers to relative rotation between the adjusting screw and the spindle tube. A knob means is attached to the adjusting screw exteriorily of the support column in order to afford a means by which to overcome the aforesaid resistance to relative rotation offered by the bushing in order to permit selective adjustment in the height of the seat section with respect to the base portion of the seat.

United States Patent Good Dec. 2, 1975 [75] Inventor: Wayne W. Good,Sturgis, Mich.

[73] Assignee: Harter Corporation, Sturgis, Mich.

[221 Filed: Mar. 21, 1975 i [211 App]. No.: 560,580

[52] U.S. Cl. 248/405; 248/415; 297/347 [51] Int. Cl. F16M 13/00 [58]Field of Search 248/405, 406, 161, 415; 297/347, 348; 108/141 [56]References Cited UNITED STATES PATENTS 526,045 9/1894 Morgan 248/415 X682,844 9/1901 Ellenbecker.. 248/405 1,242,110 10/1917 Koken i 248/4052,219,814 10/1940 Jones 108/141 3,799,486 3/1974 Mohr et al. 248/406Primary Examiner-Roy D. Frazier Assistant Examiner-Robert W. Gibson, Jr.Attorney, Agent, or FirmHami1ton, Renner & Kenner [57] ABSTRACT Anadjustable support column for pivotally mounting the seat section of achairto the base portion thereof. The nave of the base portion has anupwardly flared bore into which the lower, tapered end portion of asheath tube is supportingly received. A thrust bearing is mounted insidethe lower end portion of the sheath tube and rotatably supports anadjusting screw. The

-- seat section has a conical spindle that is received within a conicalsocket at the upper end of the spindle tube. A bushing is fixed to thelower end portion of the spindle tube and is threaded onto the adjustingscrew. The bearing and bushing are selected such that the bearing offersless resistance to relative rotation between the adjusting screw and thesheath tube than the bushing offers to relative rotation between theadjusting screw and the spindle tube. A knob means is attached to theadjusting screw exteriorily of the support column in order to afford ameans by which to overcome the aforesaid resistance to relative rotationoffered by the bushing in order to permit selective adjustment in theheight of the seat section with respect to the base portion of the seat.

6 Claims. 4 Drawing Figures US. Patent Dec. 2, 1975 Sheet 1 of23,923,280

US. Patent Dc.2,1975 Sheath 2 3,923,280

ADJUSTABLE SUPPORT COLUMN FOR A PIVOTAL CHAIR BACKGROUND OF THEINVENTION The present invention relates generally to an adjustablesupport column for pivotally mounting the seat section of a chair to abase portion.

Historically, adjustment in the height of a seat has been accomplishedby the use of a threaded spindle that becomes progressively exposed asthe seat is raised by threading the spindle upwardly out of the bell nutand hub tube.

In response to considerations of: improving the operating efficiency (byshielding the threaded portion of the spindle from deleterious dust anddirt); providing an aesthetically improved appearance (by shielding thethreaded spindle from view); and, maintaining cleanliness (by shieldingthe person using the chair, and his or her clothes, from the lubricantemployed on the threaded spindle), various types of cover assemblies andconcomitant mechanisms for permitting selective height adjustabilityhave been provided.

One approach has necessitated the incorporation of a special connectionbetween the seat section of the chair and the threaded spindle often byinserting a pivot therebetween in order to permit the seat section to berotated without effecting an adjustment in the height of the seat.

Another approach has necessitated some physical connection between thecover assembly and the adjusting mechanism hidden thereby. Butirrespective of the approach, the structure has generally required theuse of an axially slotted adjusting screw and a J-washer to determinerotation between the adjusting screw and various other parts of theheight adjusting mechanism, as required selectively to adjust the heightof the seat section with respect to the base portion.

Moreover, the more complex the structure of the support column becomesto effect the desired objectives of providing an efficient, aestheticand clean height adjusting column, the more tedious and expensive itbecomes to manufacture and maintain the support column.

SUMMARY OF THE INVENTION It is, therefore, a primary object of thepresent invention to provide an improved support column for pivotallymounting the seat section of a chair to the base portion.

It is another object of the present invention to provide an improvedsupport column, as above, which employs an adjusting screw that does notneed to be longitudinally slotted and which does not employ thecustomary J-washer.

It is yet another object of the present invention to provide an improvedsupport column, as above, that can be completely assembled anddisassembled with facility, thereby allowing the chair to occupy theminimum volume of space for shipment in its knockeddown state and to beassembled at the point of use without the need for tools.

It is a further object of the present invention to provide an improvedsupport column, as above, which can, because of the facility with whichit can be assembled and disassembled, be readily converted from a highbase to a low base chair, or vice versa.

It is a still further object of the present invention to provide animproved support column, as above, in which the threaded adjusting screwis shielded from view and no lubricant is required on the adjustingscrew itself.

It is an even further object of the present invention to provide animproved support column, as above, that is not only uncomplicated butrelatively inexpensive to manufacture and maintain.

These and other objects, together with the advantages thereof overexisting and prior art forms which will become apparent from thefollowing specification, are accomplished by means hereinafter describedand claimed.

In general, a chair embodying the concept of the present invention has abase portion comprising a plurality of legs radiating from the navethereof. A collet with an upwardly flared bore is secured within thenave of the base portion supportingly to receive the conically tapered,lower end portion of a sheath tube. A thrust bearing is mountedinteriorily of the sheath tube at its lower extremity, and the thrustbearing rotatably supports an adjusting screw.

A knob is presented from the end of the adjusting screw which, thoughaxially fixed within the thrust bearing, extends downwardly through thethrust bearing to be accessible at a location immediately beneath thenave. Upwardly with respect to the thrust bearing the adjusting screw isthreaded along substantially its entire length.

A tapered spindle is secured to the underside of the seat section and isreceived within a tapered socket in,

the upper end of the spindle tube. The spindle tube extendsconcentrically within the sheath tube, and an annular bushing is securedin the lower end portion of the spindle tube. The interior of thebushing is threaded to be received on the threaded portion of theadjusting screw. The bushing is fabricated so that the resistance torelative rotation between the adjusting screw and the spindle tube isgreater than the resistance afforded by the thrust bearing againstrelative rotation of the adjusting screw with respect to the sheathtube. As such, the seat section may freely rotate with respect to thebase portion of the chair without effecting any adjustment in the heightof the chair. Yet, by rotating the seat section while grasping the knobto preclude rotation of the adjusting screw or by manipulating the knobto rotate the adjusting screw while holding the seat section againstrotation, one can effect relative rotation between the adjusting screwand the spindle tube in order to adjust the height of the seat sectionwith respect to the base portion.

One preferred embodiment of an adjusting support column for a pivotallymounted chair embodying the concept of the present invention is shown byway of example in the accompanying drawings without attempting toshow'all of the various forms and modifications in which the inventionmight be embodied; the invention being measured by the appended claimsand not by the details of the specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a frontal-side perspective of achair embodying the concept of the present invention, the seat sectionand the support column being exploded vertically with respect to thebase portion in order to reveal the interrelation of those componentsprior to field assembly;

FIG. 2 is an enlarged side elevation of a chair embodying the concept ofthe present invention, the seat section, support column and base portionbeing disposed in their normal operative position and the base beingpartially broken away to reveal the disposition of the support columnwith respect thereto;

FIG. 3 is a further enlarged vertical section taken substantially alongline 33 of FIG. 2; and,

FIG. 4 is a horizontal section taken substantially along line 44 of FIG.3.

DESCRIPTION OF A PREFERRED EMBODIMENT A support column embodying theconcept of the present invention is designated generally by the numeralon the appended drawings and provides means for adjusting the height ofa seat section 11 with respect to a base portion 12 in a chair 13.

The base portion 12 may comprise a plurality of radially extending legs14 that are conjoined at the nave 15 to support a collet 16 whichextends vertically therethrough and which presents an upwardly flaredbore 18. The radially outer extremity of each leg 14 may be providedwith casters 19, as shown.

The support column 10 has an outer sheath, or casing, tube the lower endportion of which is tapered, as at 21, to be matingly received withinand supported by the flared bore 18 in collet 16. The lower extremity ofthe sheath tube 20 is directed radially inwardly to present an annularcavity 22 and an annular supporting flange 23, the latter comprising thelower wall of cavity 22. The supporting flange 23 should havesubstantial strength because it will be required to support the fullweight of the seat section 11 and anyone or anything resting thereon.

A thrust bearing is removably insertable within the cavity 22 accuratelyto position the thrust bearing 25, and the stationary element 24 of thethrust bearing 25 is carried on the supporting flange 23. An adjustingscrew 27 is captured within the moving element 26 of the thrust bearing25 to be rotatable therewith, and in order to assure a fixed verticaldisposition of the adjusting-screw 27 with respect to the thrust bearing25, one may preferably employ a positioning rib 28 that circumscribesthe shaft 29 of the adjusting screw 27. Although the cylindrical lowerend portion 30 of the shart 29 is preferably press fit through the bore31 of the moving element 26, the positioning rib 28 maintains thedesired relative vertical disposition of the adjusting screw 27 withrespect to the thrust bearing 25 such that the cylindrical lower endportion 30 of the shaft 29 extends through the bearing 25 andteriminates below the collet 16 in order to permit a control knob 32 tobe secured thereto, as by the set screw 33, and to permit manual accessto the knob 32 immediately beneath the nave 15.

That portion of the shaft 29 which extends vertically upwardly of thepositioning rib 28 is provided with external threads 34. An annularbushing 35 is provided with internal threads 36 which allow the bushing35 to be screwed onto and along the threads 34 of shaft 29. Thecylindrical outer surface 37 of the bushing 35 is secured within thecylindrical inner wall 38 at the lower end portion 39 of a spindle tube40.

The upper end portion 41 of the spindle tube presents a flared socket 43into which the tapered spindle 45 of the seat section 11 issu'pportingly received. As best seen in FIG. 2, the spindle 45 issecured to rotate with the seat section by staking, press-fitting, orotherwise securing the spindle 45 to a chair control 46 presented fromthe underside of the seat section 11.

A bearing liner 48 has an elongate, annular sleeve portion 49 thatembraces the spindle tube 40. A plurality of ribs 50 extendlongitudinally along the outer surface 51 of the sleeve portion 49. Theribs 50 project radially outwardly from the sleeve portion 49 to engagethe radially inner wall 52 of the sheath tube 20 and thereby maintainthe spindle tube 40 concentrically with respect to the sheath tube 20.In order to minimize frictional resistance between the spindle tube 40and the sleeve portion 49, at least the sleeve portion 49 of the bearingliner 48 is preferably made of a selflubricating plastic such as Zytel.

Before discussing the adjustable features of the chair 13 it should beappreciated that the tapered coupling arrangement by which the supportcolumn 10 is secured to the base portion 12 and the tapered couplingarrangement by which the seat section 11 is mounted on the supportcolumn 10 allow the three basic components of the chair to be assembledand disassembled with facility. This feature not only makes it quiteeasy to repair the chair but also permits the chair to be shippeddisassembled and allows extremely rapid assembly without requiring anytools.

In addition, the component parts of the support column 10 may also bereadily assembled and disassembled. For example, if one selects a thrustbearing unit 25 having a diameter less than the internal diameter of thesleeve portion 49 presented by the bearing liner 48, the thrust bearing25, the adjusting screw 27 and the spindle tube 40 may, upon removal ofthe control knob 32, be extracted as a unit upwardly through the liner48. This capability not only allows ready replacement of any partswithin the support column 10 but also permits any chair to be changedfrom a low base to a high base, or vice versa, simply by providingsubstitute sheath tubes 20 and spindle tubes 40 of appropriate length.As should now be appreciated, these components can be interchanged withrelative ease.

As depicted in FIG. 3, the bushing 35 appears to have a greater axialextent and might initially appear to be required. Yet this protractedaxial extent serves the very crucial functional purpose of providingmore resistance to rotation between the bushing 35 and the adjustingscrew 27 than exists between the stationary and moving elements 24 and26, respectively, of the thrust bearing 25. Thus, irrespective ofwhether the chair is empty or filled, rotation of the seat section 11with respect to the base portion 12 effects relative motion between theelements of the thrust bearing 25 rather than between the bushing 35(non-rotatably secured to the spindle tube 40) and the adjusting screw27 so long as the control knob 32 is free to rotate. When, however,relative rotation occurs between the control knob 32 and the seatsection 11, the bushing 35 will travel along the threads 34 on the shaft29 of the adjusting screw 27 to raise, or lower, the seat section 11with respect to the base portion 12 depending on the relative rotationaldirection between the adjusting screw 27 and the bushing 35.

It should now be apparent that a pivotal chair employing an improvedsupport column embodying the concept of the present invention can bereadily assembled and disassembled, is relatively uncomplicated andotherwise accomplishes the objects of the invention.

What is claimed is:

1. An adjustable support column for pivotally mounting the seat sectionof a chair to a base portion comprising: a sheath tube extendingupwardly from the base portion; bearing means carried by said sheathtube; an adjusting screw supported by said bearing means for rotationrelative to said sheath tube; knob means to control rotation of saidadjusting screw; a spindle tube supporting the seat section extendingdownwardly therefrom; a bushing fastened to said spindle tube andthreaded onto said adjusting screw to rotate with and with respectthereto; and, means to assure that the resistance to relative rotationbetween said bushing and said adjusting screw exceeds the resistance torelative rotation between said adjusting screw and said sheath tube.

2. An adjustable support column, as set forth in claim 1, in which saidspindle tube is insertable axially within said sheath tube and means areprovided slidably to support said spindle tube concentrically withrespect to said sheath tube.

3. An adjustable support column, as set forth in claim 2, in which thelower end portion of said sheath tube is directed radially inwardly topresent an annular cup and supporting flange, said bearing means beingremovably positioned within said cup and carried on said supportingflange.

4. An adjustable support column, as set forth in claim 3, in which saidknob means is demountably secured to said adjusting screw and thediameter of said bearing means is of lesser dimension than the internaldiameter of the means slidably to support said spindle tubeconcentrically with respect to said sheath tube.

5. An adjustable support column, as set forth in claim 1, in which saidbase portion comprises a plurality of leg members extending radiallyoutwardly from a nave, a conically upwardly flared bore presented fromsaid nave, the lower end portion of said sheath tube being conicallytapered to be supportingly received within said flared bore.

6. An adjustable support column, as set forth in claim 1, in which aconically tapered spindle is secured to and extends downwardly from saidseat section, a conically flared socket is presented from the upper endportion of said spindle tube, said spindle being supportingly receivedwithin said socket.

1. An adjustable support column for pivotally mounting the seat sectionof a chair to a base portion comprising: a sheath tube extendingupwardly from the base portion; bearing means carried by said sheathtube; an adjusting screw supported by said bearing means for rotationrelative to said sheath tube; knob means to control rotation of saidadjusting screw; a spindle tube supporting the seat section extendingdownwardly therefrom; a bushing fastened to said spindle tube andthreaded onto said adjusting screw to rotate with and with respectthereto; and, means to assure that the resistance to relative rotationbetween said bushing and said adjusting screw exceeds the resistance torelative rotation between said adjusting screw and said sheath tube. 2.An adjustable support column, as set forth in claim 1, in which saidspindle tube is insertable axially within said sheath tube and means areprovided slidably to support said spindle tube concentriCally withrespect to said sheath tube.
 3. An adjustable support column, as setforth in claim 2, in which the lower end portion of said sheath tube isdirected radially inwardly to present an annular cup and supportingflange, said bearing means being removably positioned within said cupand carried on said supporting flange.
 4. An adjustable support column,as set forth in claim 3, in which said knob means is demountably securedto said adjusting screw and the diameter of said bearing means is oflesser dimension than the internal diameter of the means slidably tosupport said spindle tube concentrically with respect to said sheathtube.
 5. An adjustable support column, as set forth in claim 1, in whichsaid base portion comprises a plurality of leg members extendingradially outwardly from a nave, a conically upwardly flared borepresented from said nave, the lower end portion of said sheath tubebeing conically tapered to be supportingly received within said flaredbore.
 6. An adjustable support column, as set forth in claim 1, in whicha conically tapered spindle is secured to and extends downwardly fromsaid seat section, a conically flared socket is presented from the upperend portion of said spindle tube, said spindle being supportinglyreceived within said socket.